ROX-30728: add fallback to internal k8s svc for FM/FS k8s auth

[johannes94]

Description

This PR changes the KubernetesIssuer for FM <> FS auth.

Current behavior:

• Fetch the openid configuration
• Fetch the JWKS from the url given in that configuration

New behavior:

• Fetch the openid configuration
• Try to fetch the JWKS from the URL given in that config
• If it fails try kubernetes.default.svc as a Host instead

This is required as a step to use ROSA HCP for e2e test, because infra ROSA HCPs do not publicly expose the JWKS given in the openid configuration, but using the internal svc works.

Checklist (Definition of Done)

• Unit and integration tests added
• Added test description under Test manual
• Documentation added if necessary (i.e. changes to dev setup, test execution, ...)
• CI and all relevant tests are passing
• Add the ticket number to the PR title if available, i.e. ROX-12345: ...
• Discussed security and business related topics privately. Will move any security and business related topics that arise to private communication channel.
• Add secret to app-interface Vault or Secrets Manager if necessary
• RDS changes were e2e tested manually
• Check AWS limits are reasonable for changes provisioning new resources
• (If applicable) Changes to the dp-terraform Helm values have been reflected in the addon on integration environment

Test manual

TODO: Add manual testing efforts

# To run tests locally run:
make db/teardown db/setup db/migrate
make ocm/setup
make verify lint binary test test/integration

[kovayur]

The change looks good and covers more use cases. One question: Can we remove the override defined in getJwksURI and only rely on the new one?

[johannes94]

@kovayur Applied the suggested changes, thanks.

[kovayur]

👍

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: johannes94, kovayur

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